Chemical vapor deposition (CVD) is a critical component in semiconductor manufacturing. CVD occurs when a stable compound is formed by a thermal reaction or decomposition of certain gaseous chemicals and such compounds are deposited on a surface. CVD systems come in many forms. One apparatus for such a process comprises a conveyorized atmospheric pressure CVD (APCVD) system which is described in U.S. Pat. No. 4,834,020 and is owned by assignee. This patent is incorporated herein by reference. Other CVD apparatus may be used such as plasma-enhanced CVD (PECVD) systems, and low pressure CVD (LPCVD) systems.
One critical component of CVD systems is the injector utilized for delivering gaseous chemicals to the surface. The gases must be distributed over the substrate, so that the gases react and deposit an acceptable film at the surface of the substrate. A function of the injector is to distribute the gases to a desired location in a controlled manner. Controlled distribution of the gases maximizes the chance of complete, efficient and homogeneous reaction of the gases, in part by minimizing pre-mixing and prior reaction of the gases. A complete reaction provides a greater opportunity for a good quality film. If the gas flow is uncontrolled, the chemical reaction will not be optimal and the result will likely be a film which is not of uniform composition. When the film is not of uniform composition, the proper functioning of the semiconductor is impaired. Thus it is important that an injector design facilitates the desired flow of the gases in a controlled manner.
In a prior art injector, owned by the assignee and described in U.S. Pat. No. 5,136,975, a number of stacked plates each including a number of linear hole arrays is utilized. The plates produce a number of cascaded hole arrays and a chute surrounded by a cooling plate is positioned beneath the last hole array. The chute includes a central passage and ducts are formed between the chute and the cooling plate. Chemical lines deliver gases to a top plate which discretely conveys the gases to the top of individual cascaded hole arrays. The gases are fed through cascaded hole arrays which cause the gas to flow in an increasingly uniform manner. The chute passage receives the gases individually and then conveys the gases to a region above a wafer. In this region, the gases mix, react and then form a film or layer on the wafer.
The cascading action described above provides an uniformly distributed gas flow. However, flow control and simplicity of injector design can be improved.